Diagnosis of Stones

Intravenous Pyelogram (IVP) and Tomography

IntraVenous Pyelogram (IVP), also referred to as intravenous urogram (IVU) or EXcretory Urography (EXU) has been the modality of choice for radiographic evaluation of patients with suspected urinary calculi. IVP can verify the presence of a calcification on a plain radiography that is within the ureter and also delineates the anatomical relationship of the urinary tract to the calcification. The collection of contrast within the urinary tract is able to identify the presence of a urinary tract stone and the presence or absence of obstruction. Obstruction by the stone or calcification is evident by delayed opacification of the affected kidney and collecting system while the normal kidney (opposite or contralateral kidney) already has relatively reduced opacification by the excretion of contrast from the kidney.

Normal IVP. Ten-minute excretory urogram shows normal kidneys, ureters and contrast filling of the bladder.

Plain film tomography is utilized to increase the recognition of renal masses, fine renal calcifications and paranephric structures. The tomograms should be obtained just before or just after the 3-minute films, usually 8cm to 10cm from the posterior abdominal wall (or table top) to ensure a satisfactory nephrogram and early calyceal filing.
Normal kidneys. Tomogram demonstrates the presence of the right and left kidney (yellow arrowheads).

Advantages of IVP

  1. Identifying the anatomical relationship of the urinary tract system to the calcification.
  2. Demonstrate the presence for absence of urinary tract obstruction.
  3. Good survey of the urinary tract system.
  4. Can evaluate the contralateral kidney.

Disadvantages of IVP

  1. Missing small stones.
  2. The passage of stones causing edema or swelling at the UVJ mimicking the appearance of a retained stone.
  3. Risks associated with intravenous contrast (adverse reactions including anaphylaxis, pruritus and renal failure).
  4. Exposure to ionizing radiation.
  5. Quality of study may be limited by inadequate bowel preparation, bowel ileus, swallowed air and technician variability.
  6. Inconvenience of a long filming sequence.
  7. If IVP is negative for obstruction calculus, it may fail to adequately diagnosis other extraurinary causes of acute flank pain.

A dye is injected into the patient's vein. The dye is collected within the urinary tract system. This dye is visible on x-ray. A series of x-rays are obtained before (scout film) and after contrast is injected. The dye allows the physician to determine the location of the stone, the presence of obstruction, the anatomy of the urinary tract and whether the stone is radiolucent or radio-opaque.

Suggested readings
Yilmaz S, Sindel T, Arslan G, et al: Renal colic: Comparison of spiral CT, US and IVU in the detection of ureteral calculi. Eur Radiol 1998; 8(2): 212-217.

Laing FC, Jeffrey RB Jr, Wing VW: Ultrasound versus excretory urography in evaluating acute flank pain. Radiology 1985; 154(3):613-616.

Svedstrom E, Alanen A, Nurmi M: Radiologic diagnosis of renal colic: The role of plain films, excretory urography and sonography. Eur J Radiol 1990; 11(3): 180-183.

 

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